Issue 43

D. Gentile, Frattura ed Integrità Strutturale, 43 (2018) 155-170; DOI: 10.3221/IGF-ESIS.43.12 160 a) b) Figure 4: Examples of ENF responses for ductile and brittle matrix. Thus, the fracture toughness is calculated from the following beam theory expression:           2 2 3 3 9 4 1 1.5 / SH IIc a P C C G wL a L (16) where    3 2 13 6 3 / 20 SH L a L a C whG (17) In the EN6034 prescription the nomenclature is slightly different and in particular the entire span is L*=2L. Consequently, Eqn. (11) becomes:    2 *3 3 9 2 (0.25 3 ) II P a G w L a (18) E XPERIMENTAL TECHNIQUE quasi-static electro-mechanical traction machine GALDABINI SUN10/P has been used for the testing. During each test, both the crosshead displacement and the applied load have been recorded. Preliminary system calibration has also been performed particularly to check the behavior of the two hinges used in the DCB test configuration and the bonding technique used to apply them to the specimens. The material investigated is a carbon fiber/epoxy unidirectional laminate with different configurations in terms of resin volume and cure or fiber. Initially, DCB and ENF samples from different laminate types have been produced, examined, and identified according to the nomenclature given in Tab. 1. Investigated materials are very close to commercial T1000 and M30 produced by TORAYCA®, at the moment is not allowed to the author to give further indications. A total of 61 tests have been performed. DCB hinges selection and assessment As far as concerns the DCB configuration tests, load has been applied by means of two hinges as suggested in the ASTM prescriptions, Fig. 5, [13]. A